1. Field of the Invention
The present invention relates to a voice input apparatus which is applied to a mobile phone, a recording device and the like, for example, and more particularly, relates to a structure of a voice input apparatus that includes a microphone unit which is so formed as to allow a sound pressure to act on both surfaces (front and rear surfaces) of a diaphragm and obtains a voice signal by using a vibration of the diaphragm based on a sound pressure difference.
2. Description of Related Art
Conventionally, a voice input apparatus is used for, for example, voice communication devices such as a mobile phone, a transceiver and the like, or for information process systems such as a voice identification system and the like which use a technology for analyzing an input voice, or for a recording device and the like. For over-the-telephone talking, voice recognition and voice recording, it is preferable that only a target voice (user's voice) is collected. For this purpose, a voice input apparatus which accurately extracts a target voice and removes noise (background noise and the like) other than the target voice is being developed.
As a technology which in a use environment where noise is present, removes noise and collects a target voice only, there is a technology for providing a microphone of a voice input apparatus with directivity. As an example of a microphone which has directivity, a microphone unit which is so formed as to allow a sound pressure to act on both surfaces of a diaphragm and obtains a voice signal by a vibration of the diaphragm based on a sound pressure difference is conventionally known (e.g., see patent documents 1 and 2).
Incidentally, conventionally, a microphone unit which a voice input apparatus includes is equipped with an electric circuit portion that processes (e.g., amplification process and the like) an electric signal which is generated based on a vibration of a diaphragm. And, conventionally, this electric circuit is disposed outside a sound guide space which extends from a sound hole to a diaphragm (e.g., see FIG. 2 of the patent document 2).
[Patent document 1] JP-A-1992-217199
[Patent document 2] JP-A-2005-295278